CA1105918A - Rubber accelerators - Google Patents
Rubber acceleratorsInfo
- Publication number
- CA1105918A CA1105918A CA304,852A CA304852A CA1105918A CA 1105918 A CA1105918 A CA 1105918A CA 304852 A CA304852 A CA 304852A CA 1105918 A CA1105918 A CA 1105918A
- Authority
- CA
- Canada
- Prior art keywords
- composition according
- benzothiazole sulfenamide
- oxirane
- dimorpholine
- benzothiazole
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
- C08K5/43—Compounds containing sulfur bound to nitrogen
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/15—Heterocyclic compounds having oxygen in the ring
- C08K5/151—Heterocyclic compounds having oxygen in the ring having one oxygen atom in the ring
- C08K5/1515—Three-membered rings
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
- C08K5/45—Heterocyclic compounds having sulfur in the ring
- C08K5/46—Heterocyclic compounds having sulfur in the ring with oxygen or nitrogen in the ring
- C08K5/47—Thiazoles
Abstract
26,749 TITLE OF THE INVENTION
SULFENAMIDE ACCELERATORS
STABILIZED WITH OXIRANE COMPOUNDS
ABSTRACT OF THE DISCLOSURE
Oxirane compounds having a molecular weight greater than 60 have been found to be effective stabilizers for sulfenamide rubber accelerators.
SULFENAMIDE ACCELERATORS
STABILIZED WITH OXIRANE COMPOUNDS
ABSTRACT OF THE DISCLOSURE
Oxirane compounds having a molecular weight greater than 60 have been found to be effective stabilizers for sulfenamide rubber accelerators.
Description
9~8 N,N'-[(thiocarbonyl)thio]dimorpholine and 2-benzothiazole sulfenamide are rubber accelerators which are widely used in the rubber industry. While the compounds are readily prepared according to well-known procedures in a high state of purity, they deteriorate when exposed to elevated temperatures and/or humid conditions. The deterioration of the sulfenamides is manifested by a gradual build-up of mercaptobenzothiazyl disulfide (MBTS) resulting in an alteration of the cure characteristics normally exhibited by the accelerator when used in a rubber vulcanizate.
Since elevated temperatures and humid conditions are common in the summer months and throughout the warmer areas of the world, it is desirable to find a means for either stopping or retarding this deterioration without destroying the accelerating activity of the compounds.
It has now been found that the incorporation of a minor amount of a oxirane (epoxy) compound into the N,N'-[(thiocarbonyl)thio] dimorpholine and the benzothiazole sulfenamides significantly reduces the deterioration of the accelerators on exposure to temperature and/or humidity.
Accordingly, the present invention provides a stabilised accelerator composition for rubber comprising (1) N,N'-[(thiocarbonyl)thio]
dimorpholine or a benzothiazole sulfenamide having the formula:
~ C - S - (S)~ - N \
wherein R and R' are, individually, hydrogen, alkyl i 1 - 8 carbon atoms, inclusive, cycloaIkyl of 5 - 6 carbon atoms, inclusive or taken with the nitrogen, combine to form a heterocyclic ring, and n is 0 or 1 and (2) an effective stabilizing amount of an oxirane compound free of interfering functional groups and having a molecular weight greater than 60.
Since elevated temperatures and humid conditions are common in the summer months and throughout the warmer areas of the world, it is desirable to find a means for either stopping or retarding this deterioration without destroying the accelerating activity of the compounds.
It has now been found that the incorporation of a minor amount of a oxirane (epoxy) compound into the N,N'-[(thiocarbonyl)thio] dimorpholine and the benzothiazole sulfenamides significantly reduces the deterioration of the accelerators on exposure to temperature and/or humidity.
Accordingly, the present invention provides a stabilised accelerator composition for rubber comprising (1) N,N'-[(thiocarbonyl)thio]
dimorpholine or a benzothiazole sulfenamide having the formula:
~ C - S - (S)~ - N \
wherein R and R' are, individually, hydrogen, alkyl i 1 - 8 carbon atoms, inclusive, cycloaIkyl of 5 - 6 carbon atoms, inclusive or taken with the nitrogen, combine to form a heterocyclic ring, and n is 0 or 1 and (2) an effective stabilizing amount of an oxirane compound free of interfering functional groups and having a molecular weight greater than 60.
2-Benzothiazole sulfenamides may be represented by the general formula S - (S)n - N
N R' - ,~
~s~
wherein R and R' individually represent hydrogen, alkyl of 1 to 8 carbon atoms, inclusive, cycloaIkyl of 5 to 6 carbon atoms, inclusive, or taken together with the nitrogen atom, combine to form a heterocyclic ring, and n is O or 1. They - la -_i 1 are readily prepared by well-known procedures, see for ex-ample, United States Patent Nos. 2,730,526; 2,730,527;
2,758,995; 2,776,297; 2,840,556; 2,981,325; 3,055,909;
N R' - ,~
~s~
wherein R and R' individually represent hydrogen, alkyl of 1 to 8 carbon atoms, inclusive, cycloaIkyl of 5 to 6 carbon atoms, inclusive, or taken together with the nitrogen atom, combine to form a heterocyclic ring, and n is O or 1. They - la -_i 1 are readily prepared by well-known procedures, see for ex-ample, United States Patent Nos. 2,730,526; 2,730,527;
2,758,995; 2,776,297; 2,840,556; 2,981,325; 3,055,909;
3,161,648; and 3,658,808. Some of the more commonly used accelerators include N-isopropyl-2-benzothiazole sulfenamide;
N,N-diisopropyl-2-benzothiazole sulfenamide; N-t-butyl-2--benzothiazole sulfenamide; N-cyclohexyl-2-benzothiazole sul-fenamide; N,N-dicyclohexyl-2-benzothiazole sulfenamide; N-oxy-diethylene-2-benzothiazole sulfenamide; 4-morpholinyl-2-benzo-thiazole disulfide; N-t-octyl-2-benzothiazole sulfenamide;
N,N-dicyclopentyl-2-benzothiazole sulfenamide; N,N-diethyl-2--benzothiazole sulfenamide; N-methyl-2-benzothiazole sulfen-amide and the like.
N,N'-[(thiocarbonyl)thio]dimorpholine is an old compound. It can be readily made by reacting sodium 4-mor-pholinocarbodithioate (II) with N-chloromorpholine (III):
. . _ ~ _ ~ C S Na ~ Cl N 3 >
20 (II) (III) ~ S
O N C - S ~ ~ NaCl Another method is described whereby (II) is react-ed with morpholine and an oxidizing agent such as an aqueous solution of iodine and potassium iodide or sodium hypochlor-ite or other oxidizing agent known in the art for the prepara-tion of thiocarbonylsulfides.
Use of the compound as an accelerator is described 1 by Taylor, Rubber Chem. ~ Tech. 47 (No. 4), 906-910 (1974).
The oxirane compounds which are useful herein are those solid or liquid organic oxirane compounds having a molecular weight of greater than about 60 and have no func-tional groups reactive with the dimorpholine and sulfenamideother than the oxirane ring. These compounds include, but are not limited to, alkyl, cycloalkyl and aryl glycidyl ethers;
mono- and diepoxidized alkenes and dienes, including epoxi-dized diene polymers, such as, for example, 1,2- and 2,3--epoxybutane and epoxidized polybutadiene; cycloalkylene ox-ides such as cyclohexene oxide, vinyl cyclohexene diepoxide, etc.; diglycidyl ethers of aliphatic diols such as the di-glycidyl ether of 1,4-butanediol; diglycidyl ethers of bis-phenols such as the diglycidyl ether of isopropylidene bis-phenol (Bisphenol A) or diglycidyl ethers of methylene bis-phenol and oligomers thereof; epoxidized oils such as epoxi-dized linseed oil, etc.; epoxidized unsaturated diglycidyl ethers of polymeric diols and polyglycidyl ethers of polyols and the like.
In practicing the invention, the N,N'-[(thiocar-bonyl)thio]dimorpholine or the sulfenamide is blended in any convenient manner consistent with the invention with the oxi-rane compound. Since N,N'-[(thiocarbonyl)thio]dimorpholine is not very stable, the procedure used to blend it with the oxirane should avoid exposure to elevated temperatures for too long a period of time. Nevertheless, one method of pro-ducing the blend is to melt the N,N'-[(thiocarbonyl)thio]-dimorpholine, blend in the appropriate oxirane compound, allow the molten blend to cool and either flake or grind the resultant solid for use. Alternatively, the oxirane and P~5~
1 dimorpholine may be dry blended. The blending method is not critical to the invention; however, it will be understood that not all stabilizer compounds will melt or dissolve into the molten accelerator and dispersions may sometimes result, and that, in some instances, it may be better to dry blend and vice versa.
The sulfenamides are often prepared by cooling and flaking the molten compound. In this case, it is possible to incorporate the oxirane compound into the melt before cooling and flaking.
The blends may be prepared in any weight ratio without incident, but the oxirane concentration should range from about 0.1 percent, by weight, to about 5.0 percent, by weight, depending on the particular stabilizer, it being realized that the stabilizers may vary in their effective-ness in stabilizing the accelerator compound. Preferably, the dimorpholine or the sulfenamide may be effectively stab-ilized against deterioration on aging using about 0.5 to 3 percent, by weight, of the oxirane compound, based on the weight of the dimorpholine or sulfenamide.
Stabilization, as defined for the purposes of this invention, means any significant improvement in the stability of the N,N'-[(thiocarbonyl)thio]dimorpholine or the sulfen-amide after storing for a period of time at normal room temp-erature or at an elevated temperature. An accelerated agingtest which excemplifies the stabilization of the dimorpholine is defined hereinbelow. Improvement in stability means any significant reduction of the loss of cure rate experienced by use of the unstabilized dimorpholine during a similar per-iod of storage under the same conditions, and/or any signif-~`5~
l icant decrease in the loss of scorch protection (scorchtime) relative to the unstabilized dimorpholine. The un-stabilized compound ordinarily suffers degradation on stor-age over a period of time such that its use in a vulcaniza-tion results in a slower rate of cure and oftentimes a re-duction in scorch time. This is often manifested in the vulcanized rubber product by slower development of the optimum modulus properties and in many cases the extent of the full cure may be afffcted, i.e., the optimum properties may not be attained.
Cure rate is determined by use of a Monsanto Oscillating Disc Rheometer and is reported as the maximum slope of the cure curve in inch-pounds per 0.5 minute oper-ating against an oscillating disc embedded in the rubber stock undergoing vulcanization.
Mooney Scorch Time is the elapsed time from the onset of the heating cycle to the start of vulcanization (induction period). With reference to the cure curve traced by the Mooney Viscometer, scorch is reported as t5, which is the time, in minutes, from one minute after the start of heating, for a five point rise in the cure curve above the minimum in the curve, at the temperature of the test, which is usually chosen to represent maximum processing temperature of the unvulcanized rubber composition.
The stabilized N,N-[thiocarbonyl)thio]dimorpholine is evaluated, as discussed above, in terms of the improvement over an unstabilized sample thereof after a period of aging.
It is difficult to determine what constitutes normal storage conditions, in terms of the physical form of storage (drums, fiber packs, paper bags, etc.), the length of storage in ~5~
1 days, weeks or months, or the temperature of storage (air--conditioned warehouses or exposure to ambient temperature in the warmer climates). In order to evaluate the effect-iveness of the stabilizers by a reasonable set of conditions, unless otherwise stated, the stabilized and unstabilized com-pounds were stored in closed containers for (a) two weeks at normal room temperature (25 - 30C.), (b) for one month at 45C., and (c) two months at 45C. The compounds were then evaluated in a standard rubber formulation as described in the following illustrative examples.
In the examples which follow, the compounds were evaluated for effectiveness of the stabilizer using the rubber masterbatch shown below (which contains 100 parts by weight of rubber stock):
Masterbatch Styrene-butadiene rubber 89.5 ;
(oil-extended) Cis-4 Polybutadiene 35.0 Aromatic oil 25.5 Carbon black 75.0 Zinc oxide 5.0 Stearic acid 1.5 N-Phenyl-N'-(1,3-dimethylbutyl)- 1.0 p-phenylenediamine Sulfur 1.8 Example 1 To a sample, comprising 100 parts of N,N-[(thio-carbonyl)thio]dimorpholine, are added 4.0 parts of 3,4-epoxy-cyclohexylmethyl-3,4-epoxycyclohexane carboxylate.
The stabilized sample is then added to the above masterbatch after storage for 6 weeks at 25~ RH and 45C., ~ ~5~
1 at a concentration of 0.9 part of stabilized sample to 100 parts of masterbatch, as described above, with compounding.
The sample is then subjected to testing in order to ascertain the accelerator activity in promoting the vul-canization reaction as measured by the cure rate and isidentified as Composition A. A sample containing no stabil-izer is set forth for comparative purposes, in Table I, be-low.
Table I
None A
Oscillating Disc Rheometer @ 316F.
Maximum Cure Rate (in.-lbs./0.5 min) 6 Weeks 3.4 3.8 Maximum Torque 15 (inch-pounds) 6 Weeks 44.5 49.5 Scorch Time (t ) Mooney Viscometer @ 270F.
(minutes) 5 6 Weeks 12.8 24.0 The data show that N,N'-t(thiocarbonyl)thio]di-morpholine is improved (stabilized against degradation) by the incorporation therein of 4.0 percent, by weight, of the epoxy compound, as shown by the retention of cure rate after storage for 6 weeks at 45C. and 25% RH and by the stability of the Mooney Scorch.
Examples 2 - 5 -The procedure of Example 1 is again followed ex-cept that the oxiranes are (B) 2.0% of epoxidized soybean oil, (C) 1.0~ of vinyl cyclohexene diepoxide, (D) 5.0% of the diglycidyl ether of 1,4-butanediol, and (E) 0.75% of a~5~
1 the diglycidyl ether of 4,4'-isopropylidenebisphenol. In each instance, effective stabilization of the N,N-[(thio-carbonyl)thio]dimorpholine is accomplished.
Example 6 Again, following the procedure of Example 1, ex-cept that the oxirane comprises 2.5~ of the diglycidyl ether of phenol-formaldehyde condensate, satisfactory stabilization is achieved.
Examples 7 - 10 When the stabilizer of Example 1 is replaced by (F) 0.5% of 2,3-epoxypropyl-n-hexylether, (G) 1.0~ of epoxi-dized butyl linseed oil, (H) 3.5% of epoxidized linseed oil, and (I) 4.0% of 2,2-bis[4-(2,3-epoxypropoxy)phenyl]propane;
effective stabilization of the accelerator is achieved.
Example 11 Stabilization of N-Isopropyl-2-Benzothiazole Sulfenamide Samples of N-isopropyl-2-benzothiazole sulfenamide are mixed with 2% of (J) 2,3-epoxypropyl-n-hexyl ether and (K) 2,2-bis[4-(2,3-epoxypropoxy)phenyl]propane. The samples are then exposed for periods of 2 weeks and 4 weeks at nor-mal room temperature and 75% humidity and then analyzed for build-up of mercaptobenzothiazyldisulfide (MBTS). The re-sults are shown below in Table II.
~n d O In ,~
~1 1 ~D
~n ~
~ a) dP 3 ~r ~ r~
r~
X ~ o o H
H
R
~ U~
E~ ~ ~
I`
~ U~ o o .Y o o o .,1 o o o ~ o o o H O O O
~1 ~ S~
e ~ ~ ~
X o 1 The data illustrate the effectiveness of the epoxy compounds in preventing deterioration of the sulfen-amide on exposure to humidity, as manifested by build-up on MBTS.
_ample 12 Samples of N-isopropyl-2-benzothiazole sulfenamide are mixed with 2% of (L) 3,4-epoxycyclohexyl methyl-3,4--epoxycyclohexane carboxylate, and (M) epoxidized butyl lin-seed oil. The samples are then exposed for periods of 2 10 weeks at 75% RH and 2 weeks at 45C./25% RH and then anal-yzed for build-up of M~TS.
Results are shown below in Table III.
i5~
N
o O O ~r U~
JJ ~ O o ,Y ,' N
A~ æl E~ ~
U~ 0~
~D O O~
~ N O
~ O O O
N
~1 N N
.,1 O O O
~ O O O
H O O O
X O N N
~1t ) ~1 ~1 ~5~
1 Example 13 A sample of N-isopropyl-2-benzothiazole sulfen-amide is mixed with 2% of (N) epoxidized linseed oil and the sample is exposed for periods of 2 weeks at 45C. and 4 weeks at 75% RH. The sample is then analyzed for build-up of MBTS.
The results are set forth in Table IV, below.
~5~
tn ~
tn In ~r ~o~ ~
Il) U~N--1 U1 .Y
u~ a U~
o~o N
U~~10 .~C ;, -''~
.
~ .
'.
,,~
H
. C~
~' ~ :: ~_I O
~: ~1 0 cn .~. -:
~ O O
; : N . ~ .
~ ~ ~ .
.,1 O O
~ O O
,1 ~ O O
a~
~1O
~ ~ :
Z
X O
1~1 .
; : ,.` ,. ; !
~!5~
1 Example 14 Stabilizaton of N,N-Diisopropyl-2-Benzothiazole Sulfenamide A sample of N,N-diisopropyl-2-benzothiazole sul-fenamide is mixed with 2% of (P) epoxidized linseed oil and then exposed for lO weeks at 45C./25% RH. The sample is then analyzed for MBTS build-up.
The results are set forth in Table V, below.
`s`~
u~
0o ~ ~a~ ..
. :
~ ~ o u~
~R
op .
u~
~ ~ o ~ o ~ o a) ~ o o E~ ~ .
E~ ,1 d~
.~dl o o ~ o o ~1 ~ o o H
a~ ~
O
S~
e X
1 Example 15 The following sulfenamides are mixed with epoxide (L), as shown in Table VI, and then exposed for periods of one week and 2 weeks at 45C./25% RH. The samples are then analyzed for MBTS build-up.
I. N-tert.butyl-2-benzothiazole sulfenamide .
~ /C -S -NH - C - C~3 II. N-oxydiethylene-w-benzothiazole sulfenamide 15 ~ ~ -S - ~
III. N-cyclohexyl-2-benzothiazole sulfenamide ~ ~ - S - N~ -Table VI
% MBTS
-ExampleInitial 1 Week 2 Weeks 5 Weeks 25 15-I 0.003 1.02 --- ---15-I+1% L0.004 0.18 --- ---15-II 0.002 0.008 0.12 3.94 15-II+3% L0.002 0.004 0.02 0.02 15-III 0.004 0.56 1.62 ---30 15-III+1% L 0.01 0.06 0.06 ---~5~
1 Examples 16-21 The procedure of Example 14P is again followed ex-cept that the epoxy compound, in each instance, is replaced by:
16. 3% of vinylcyclohexene diepoxide 17. 1.5% of styrene oxide 18. 2.0% of the diglycidyl ether of 1,4-butanediol 19. 1.0% of the diglycidyl ether of 4,4'-iso-propylidenebisphenol 20. 2.0% of the glycidyl ether of phenol-formal-dehyde condensate 21. 3.0% of epoxidized soybean oil In each instance, a substantially equivalent reduction in MBTS build-up is observed.
Examples-22-29 The procedure of Example llK is again followed except that the N-isopropyl-2-benzothiazole sulfenamide is replaced by:
22. 4-morpholinyl-2-benzothiazole disulfide 23. N,N-dicyclohexyl-2-benzothiazole sulfenamide 24. N-t-octyl-2-benzothiazole sulfenamide 25. N,N-dicyclopentyl-2-benzothiazole sulfenamide 26. N-methyl-2-benzothiazole sulfenamide 27. N-isopropyl-2-benzothiazole disulfide 28. N,N-diisopropyl-2-benzothiazole disulfide 29. N,N-diethyl-2-benzothiazole sulfenamide.
In each instance, the 2,2-bis[4-(2,3-epoxypropoxy)phenyl]-propane effectively prevented deterioration of the compounds.
N,N-diisopropyl-2-benzothiazole sulfenamide; N-t-butyl-2--benzothiazole sulfenamide; N-cyclohexyl-2-benzothiazole sul-fenamide; N,N-dicyclohexyl-2-benzothiazole sulfenamide; N-oxy-diethylene-2-benzothiazole sulfenamide; 4-morpholinyl-2-benzo-thiazole disulfide; N-t-octyl-2-benzothiazole sulfenamide;
N,N-dicyclopentyl-2-benzothiazole sulfenamide; N,N-diethyl-2--benzothiazole sulfenamide; N-methyl-2-benzothiazole sulfen-amide and the like.
N,N'-[(thiocarbonyl)thio]dimorpholine is an old compound. It can be readily made by reacting sodium 4-mor-pholinocarbodithioate (II) with N-chloromorpholine (III):
. . _ ~ _ ~ C S Na ~ Cl N 3 >
20 (II) (III) ~ S
O N C - S ~ ~ NaCl Another method is described whereby (II) is react-ed with morpholine and an oxidizing agent such as an aqueous solution of iodine and potassium iodide or sodium hypochlor-ite or other oxidizing agent known in the art for the prepara-tion of thiocarbonylsulfides.
Use of the compound as an accelerator is described 1 by Taylor, Rubber Chem. ~ Tech. 47 (No. 4), 906-910 (1974).
The oxirane compounds which are useful herein are those solid or liquid organic oxirane compounds having a molecular weight of greater than about 60 and have no func-tional groups reactive with the dimorpholine and sulfenamideother than the oxirane ring. These compounds include, but are not limited to, alkyl, cycloalkyl and aryl glycidyl ethers;
mono- and diepoxidized alkenes and dienes, including epoxi-dized diene polymers, such as, for example, 1,2- and 2,3--epoxybutane and epoxidized polybutadiene; cycloalkylene ox-ides such as cyclohexene oxide, vinyl cyclohexene diepoxide, etc.; diglycidyl ethers of aliphatic diols such as the di-glycidyl ether of 1,4-butanediol; diglycidyl ethers of bis-phenols such as the diglycidyl ether of isopropylidene bis-phenol (Bisphenol A) or diglycidyl ethers of methylene bis-phenol and oligomers thereof; epoxidized oils such as epoxi-dized linseed oil, etc.; epoxidized unsaturated diglycidyl ethers of polymeric diols and polyglycidyl ethers of polyols and the like.
In practicing the invention, the N,N'-[(thiocar-bonyl)thio]dimorpholine or the sulfenamide is blended in any convenient manner consistent with the invention with the oxi-rane compound. Since N,N'-[(thiocarbonyl)thio]dimorpholine is not very stable, the procedure used to blend it with the oxirane should avoid exposure to elevated temperatures for too long a period of time. Nevertheless, one method of pro-ducing the blend is to melt the N,N'-[(thiocarbonyl)thio]-dimorpholine, blend in the appropriate oxirane compound, allow the molten blend to cool and either flake or grind the resultant solid for use. Alternatively, the oxirane and P~5~
1 dimorpholine may be dry blended. The blending method is not critical to the invention; however, it will be understood that not all stabilizer compounds will melt or dissolve into the molten accelerator and dispersions may sometimes result, and that, in some instances, it may be better to dry blend and vice versa.
The sulfenamides are often prepared by cooling and flaking the molten compound. In this case, it is possible to incorporate the oxirane compound into the melt before cooling and flaking.
The blends may be prepared in any weight ratio without incident, but the oxirane concentration should range from about 0.1 percent, by weight, to about 5.0 percent, by weight, depending on the particular stabilizer, it being realized that the stabilizers may vary in their effective-ness in stabilizing the accelerator compound. Preferably, the dimorpholine or the sulfenamide may be effectively stab-ilized against deterioration on aging using about 0.5 to 3 percent, by weight, of the oxirane compound, based on the weight of the dimorpholine or sulfenamide.
Stabilization, as defined for the purposes of this invention, means any significant improvement in the stability of the N,N'-[(thiocarbonyl)thio]dimorpholine or the sulfen-amide after storing for a period of time at normal room temp-erature or at an elevated temperature. An accelerated agingtest which excemplifies the stabilization of the dimorpholine is defined hereinbelow. Improvement in stability means any significant reduction of the loss of cure rate experienced by use of the unstabilized dimorpholine during a similar per-iod of storage under the same conditions, and/or any signif-~`5~
l icant decrease in the loss of scorch protection (scorchtime) relative to the unstabilized dimorpholine. The un-stabilized compound ordinarily suffers degradation on stor-age over a period of time such that its use in a vulcaniza-tion results in a slower rate of cure and oftentimes a re-duction in scorch time. This is often manifested in the vulcanized rubber product by slower development of the optimum modulus properties and in many cases the extent of the full cure may be afffcted, i.e., the optimum properties may not be attained.
Cure rate is determined by use of a Monsanto Oscillating Disc Rheometer and is reported as the maximum slope of the cure curve in inch-pounds per 0.5 minute oper-ating against an oscillating disc embedded in the rubber stock undergoing vulcanization.
Mooney Scorch Time is the elapsed time from the onset of the heating cycle to the start of vulcanization (induction period). With reference to the cure curve traced by the Mooney Viscometer, scorch is reported as t5, which is the time, in minutes, from one minute after the start of heating, for a five point rise in the cure curve above the minimum in the curve, at the temperature of the test, which is usually chosen to represent maximum processing temperature of the unvulcanized rubber composition.
The stabilized N,N-[thiocarbonyl)thio]dimorpholine is evaluated, as discussed above, in terms of the improvement over an unstabilized sample thereof after a period of aging.
It is difficult to determine what constitutes normal storage conditions, in terms of the physical form of storage (drums, fiber packs, paper bags, etc.), the length of storage in ~5~
1 days, weeks or months, or the temperature of storage (air--conditioned warehouses or exposure to ambient temperature in the warmer climates). In order to evaluate the effect-iveness of the stabilizers by a reasonable set of conditions, unless otherwise stated, the stabilized and unstabilized com-pounds were stored in closed containers for (a) two weeks at normal room temperature (25 - 30C.), (b) for one month at 45C., and (c) two months at 45C. The compounds were then evaluated in a standard rubber formulation as described in the following illustrative examples.
In the examples which follow, the compounds were evaluated for effectiveness of the stabilizer using the rubber masterbatch shown below (which contains 100 parts by weight of rubber stock):
Masterbatch Styrene-butadiene rubber 89.5 ;
(oil-extended) Cis-4 Polybutadiene 35.0 Aromatic oil 25.5 Carbon black 75.0 Zinc oxide 5.0 Stearic acid 1.5 N-Phenyl-N'-(1,3-dimethylbutyl)- 1.0 p-phenylenediamine Sulfur 1.8 Example 1 To a sample, comprising 100 parts of N,N-[(thio-carbonyl)thio]dimorpholine, are added 4.0 parts of 3,4-epoxy-cyclohexylmethyl-3,4-epoxycyclohexane carboxylate.
The stabilized sample is then added to the above masterbatch after storage for 6 weeks at 25~ RH and 45C., ~ ~5~
1 at a concentration of 0.9 part of stabilized sample to 100 parts of masterbatch, as described above, with compounding.
The sample is then subjected to testing in order to ascertain the accelerator activity in promoting the vul-canization reaction as measured by the cure rate and isidentified as Composition A. A sample containing no stabil-izer is set forth for comparative purposes, in Table I, be-low.
Table I
None A
Oscillating Disc Rheometer @ 316F.
Maximum Cure Rate (in.-lbs./0.5 min) 6 Weeks 3.4 3.8 Maximum Torque 15 (inch-pounds) 6 Weeks 44.5 49.5 Scorch Time (t ) Mooney Viscometer @ 270F.
(minutes) 5 6 Weeks 12.8 24.0 The data show that N,N'-t(thiocarbonyl)thio]di-morpholine is improved (stabilized against degradation) by the incorporation therein of 4.0 percent, by weight, of the epoxy compound, as shown by the retention of cure rate after storage for 6 weeks at 45C. and 25% RH and by the stability of the Mooney Scorch.
Examples 2 - 5 -The procedure of Example 1 is again followed ex-cept that the oxiranes are (B) 2.0% of epoxidized soybean oil, (C) 1.0~ of vinyl cyclohexene diepoxide, (D) 5.0% of the diglycidyl ether of 1,4-butanediol, and (E) 0.75% of a~5~
1 the diglycidyl ether of 4,4'-isopropylidenebisphenol. In each instance, effective stabilization of the N,N-[(thio-carbonyl)thio]dimorpholine is accomplished.
Example 6 Again, following the procedure of Example 1, ex-cept that the oxirane comprises 2.5~ of the diglycidyl ether of phenol-formaldehyde condensate, satisfactory stabilization is achieved.
Examples 7 - 10 When the stabilizer of Example 1 is replaced by (F) 0.5% of 2,3-epoxypropyl-n-hexylether, (G) 1.0~ of epoxi-dized butyl linseed oil, (H) 3.5% of epoxidized linseed oil, and (I) 4.0% of 2,2-bis[4-(2,3-epoxypropoxy)phenyl]propane;
effective stabilization of the accelerator is achieved.
Example 11 Stabilization of N-Isopropyl-2-Benzothiazole Sulfenamide Samples of N-isopropyl-2-benzothiazole sulfenamide are mixed with 2% of (J) 2,3-epoxypropyl-n-hexyl ether and (K) 2,2-bis[4-(2,3-epoxypropoxy)phenyl]propane. The samples are then exposed for periods of 2 weeks and 4 weeks at nor-mal room temperature and 75% humidity and then analyzed for build-up of mercaptobenzothiazyldisulfide (MBTS). The re-sults are shown below in Table II.
~n d O In ,~
~1 1 ~D
~n ~
~ a) dP 3 ~r ~ r~
r~
X ~ o o H
H
R
~ U~
E~ ~ ~
I`
~ U~ o o .Y o o o .,1 o o o ~ o o o H O O O
~1 ~ S~
e ~ ~ ~
X o 1 The data illustrate the effectiveness of the epoxy compounds in preventing deterioration of the sulfen-amide on exposure to humidity, as manifested by build-up on MBTS.
_ample 12 Samples of N-isopropyl-2-benzothiazole sulfenamide are mixed with 2% of (L) 3,4-epoxycyclohexyl methyl-3,4--epoxycyclohexane carboxylate, and (M) epoxidized butyl lin-seed oil. The samples are then exposed for periods of 2 10 weeks at 75% RH and 2 weeks at 45C./25% RH and then anal-yzed for build-up of M~TS.
Results are shown below in Table III.
i5~
N
o O O ~r U~
JJ ~ O o ,Y ,' N
A~ æl E~ ~
U~ 0~
~D O O~
~ N O
~ O O O
N
~1 N N
.,1 O O O
~ O O O
H O O O
X O N N
~1t ) ~1 ~1 ~5~
1 Example 13 A sample of N-isopropyl-2-benzothiazole sulfen-amide is mixed with 2% of (N) epoxidized linseed oil and the sample is exposed for periods of 2 weeks at 45C. and 4 weeks at 75% RH. The sample is then analyzed for build-up of MBTS.
The results are set forth in Table IV, below.
~5~
tn ~
tn In ~r ~o~ ~
Il) U~N--1 U1 .Y
u~ a U~
o~o N
U~~10 .~C ;, -''~
.
~ .
'.
,,~
H
. C~
~' ~ :: ~_I O
~: ~1 0 cn .~. -:
~ O O
; : N . ~ .
~ ~ ~ .
.,1 O O
~ O O
,1 ~ O O
a~
~1O
~ ~ :
Z
X O
1~1 .
; : ,.` ,. ; !
~!5~
1 Example 14 Stabilizaton of N,N-Diisopropyl-2-Benzothiazole Sulfenamide A sample of N,N-diisopropyl-2-benzothiazole sul-fenamide is mixed with 2% of (P) epoxidized linseed oil and then exposed for lO weeks at 45C./25% RH. The sample is then analyzed for MBTS build-up.
The results are set forth in Table V, below.
`s`~
u~
0o ~ ~a~ ..
. :
~ ~ o u~
~R
op .
u~
~ ~ o ~ o ~ o a) ~ o o E~ ~ .
E~ ,1 d~
.~dl o o ~ o o ~1 ~ o o H
a~ ~
O
S~
e X
1 Example 15 The following sulfenamides are mixed with epoxide (L), as shown in Table VI, and then exposed for periods of one week and 2 weeks at 45C./25% RH. The samples are then analyzed for MBTS build-up.
I. N-tert.butyl-2-benzothiazole sulfenamide .
~ /C -S -NH - C - C~3 II. N-oxydiethylene-w-benzothiazole sulfenamide 15 ~ ~ -S - ~
III. N-cyclohexyl-2-benzothiazole sulfenamide ~ ~ - S - N~ -Table VI
% MBTS
-ExampleInitial 1 Week 2 Weeks 5 Weeks 25 15-I 0.003 1.02 --- ---15-I+1% L0.004 0.18 --- ---15-II 0.002 0.008 0.12 3.94 15-II+3% L0.002 0.004 0.02 0.02 15-III 0.004 0.56 1.62 ---30 15-III+1% L 0.01 0.06 0.06 ---~5~
1 Examples 16-21 The procedure of Example 14P is again followed ex-cept that the epoxy compound, in each instance, is replaced by:
16. 3% of vinylcyclohexene diepoxide 17. 1.5% of styrene oxide 18. 2.0% of the diglycidyl ether of 1,4-butanediol 19. 1.0% of the diglycidyl ether of 4,4'-iso-propylidenebisphenol 20. 2.0% of the glycidyl ether of phenol-formal-dehyde condensate 21. 3.0% of epoxidized soybean oil In each instance, a substantially equivalent reduction in MBTS build-up is observed.
Examples-22-29 The procedure of Example llK is again followed except that the N-isopropyl-2-benzothiazole sulfenamide is replaced by:
22. 4-morpholinyl-2-benzothiazole disulfide 23. N,N-dicyclohexyl-2-benzothiazole sulfenamide 24. N-t-octyl-2-benzothiazole sulfenamide 25. N,N-dicyclopentyl-2-benzothiazole sulfenamide 26. N-methyl-2-benzothiazole sulfenamide 27. N-isopropyl-2-benzothiazole disulfide 28. N,N-diisopropyl-2-benzothiazole disulfide 29. N,N-diethyl-2-benzothiazole sulfenamide.
In each instance, the 2,2-bis[4-(2,3-epoxypropoxy)phenyl]-propane effectively prevented deterioration of the compounds.
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A stabilized accelerator composition for rubber comprising (1) N,N'-[(thiocarbonyl)thio] dimorpholine or a benzothiazole sulfenamide having the formula:
wherein R and R' are, individually, hydrogen, alkyl of 1 - 8 carbon atoms, inclusive, cycloalkyl of 5 - 6 carbon atoms, inclusive, or, taken with the nitrogen, combine to form a heterocyclic ring, and n is 0 or 1 and (2) an effective stabilizing amount of an oxirane compound free of interfering functional groups and having a molecular weight greater than 60.
wherein R and R' are, individually, hydrogen, alkyl of 1 - 8 carbon atoms, inclusive, cycloalkyl of 5 - 6 carbon atoms, inclusive, or, taken with the nitrogen, combine to form a heterocyclic ring, and n is 0 or 1 and (2) an effective stabilizing amount of an oxirane compound free of interfering functional groups and having a molecular weight greater than 60.
2. A composition according to claim 1 wherein (1) is N-isopropyl-2-benzothiazole sulfenamide.
3. A composition according to claim 1 wherein (1) is N,N -diisopropyl-2-benzothiazole sulfenamide.
4. A composition according to claim 1 wherein (1) is N-cyclohexyl -2-benzothiazole sulfenamide.
5. A composition according to claim 1 wherein (2) is 2,2-bis [4-(2, 3-epoxypropoxy)phenyl] propane.
6. A composition according to claim 1 wherein (2) is epoxidized lin-seed oil.
7. A composition according to claim 1 wherein the oxirane compound is 3,4-epoxycyclohexylmethyl-3,4-epoxycyelohexane carboxylate.
8. A composition according to claim 1 wherein the oxirane is epoxidiz-ed soyabean oil.
9. A composition according to claim 1 wherein the oxirane compound is present in the range of about 0.5 to 3% by weight based on the weight of (1).
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US814,603 | 1977-07-11 | ||
| US814,601 | 1977-07-11 | ||
| US05/814,601 US4160741A (en) | 1977-07-11 | 1977-07-11 | Benzothiazole accelerators stabilized with oxirane compounds |
| US05/814,603 US4129452A (en) | 1977-07-11 | 1977-07-11 | Stabilization of N,N'-[(thiocarbonyl)thio]dimorpholine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1105918A true CA1105918A (en) | 1981-07-28 |
Family
ID=27123867
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA304,852A Expired CA1105918A (en) | 1977-07-11 | 1978-06-06 | Rubber accelerators |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS5419975A (en) |
| AR (1) | AR219326A1 (en) |
| AU (1) | AU3658378A (en) |
| BR (1) | BR7804438A (en) |
| CA (1) | CA1105918A (en) |
| DD (1) | DD137236A5 (en) |
| DE (1) | DE2827933A1 (en) |
| FR (1) | FR2397435A1 (en) |
| GB (1) | GB1599357A (en) |
| PL (1) | PL208317A1 (en) |
| SE (1) | SE7807701L (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2161160B (en) * | 1984-07-06 | 1989-05-24 | Fisons Plc | Heterocyclic sulphinyl compounds |
| JP5632592B2 (en) * | 2008-08-19 | 2014-11-26 | 株式会社ブリヂストン | Rubber composition |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3457218A (en) * | 1965-05-28 | 1969-07-22 | Bayer Ag | Cis-polybutadiene stabilized with an epoxide |
| US3658637A (en) * | 1969-03-17 | 1972-04-25 | Uniroyal Inc | Dialkyl oxalate stabilization of polyester fiber-rubber laminate against heat and chemical degradation |
| US3658743A (en) * | 1970-04-30 | 1972-04-25 | Uniroyal Inc | Stabilization of unsaturated hydrocarbon elastomers by synergistic combination of a phenolic compound an organic sulfide or thioester and an epoxide or phosphite ester |
-
1978
- 1978-05-29 AU AU36583/78A patent/AU3658378A/en active Pending
- 1978-05-31 GB GB25188/78A patent/GB1599357A/en not_active Expired
- 1978-06-06 CA CA304,852A patent/CA1105918A/en not_active Expired
- 1978-06-07 AR AR272476A patent/AR219326A1/en active
- 1978-06-26 DE DE19782827933 patent/DE2827933A1/en not_active Withdrawn
- 1978-07-10 SE SE7807701A patent/SE7807701L/en unknown
- 1978-07-10 BR BR7804438A patent/BR7804438A/en unknown
- 1978-07-11 PL PL20831778A patent/PL208317A1/en unknown
- 1978-07-11 JP JP8364778A patent/JPS5419975A/en active Pending
- 1978-07-11 FR FR7820646A patent/FR2397435A1/en active Pending
- 1978-07-11 DD DD78206653A patent/DD137236A5/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| GB1599357A (en) | 1981-09-30 |
| AR219326A1 (en) | 1980-08-15 |
| BR7804438A (en) | 1979-03-20 |
| DE2827933A1 (en) | 1979-01-25 |
| FR2397435A1 (en) | 1979-02-09 |
| AU3658378A (en) | 1979-12-06 |
| JPS5419975A (en) | 1979-02-15 |
| PL208317A1 (en) | 1979-07-02 |
| DD137236A5 (en) | 1979-08-22 |
| SE7807701L (en) | 1979-01-12 |
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